1. Field of the Invention
This invention pertains to the pouch handling art and more particularly relates to a method of evacuating air from pouches and thereafter filling the pouches with a measured quantity of air-free material.
2. Description of the Prior Art
It is well known in the art to purge air and cooking gases from flexible containers or pouches having their upper ends closed, but not sealed, by moving the containers alternately through steam and water baths during processing thereby progressively forcing noncondensible gases out of the containers before sealing the containers. Wilson U.S. Pat. No. 3,501,318, which issued on Mar. 17, 1970, and is incorporated by reference herein discloses such a process.
Wilson U.S. Pat. No. 3,528,826 which issued on Sept. 15, 1970 discloses a similar system wherein closed but unsealed pouches are alternately moved into hot water and cold water troughs to first form steam within the containers and then condense the steam to progressively drive a steam-air mixture from within the container.
U.S. Pat. No. 1,920,539 which issued to White on Aug. 1, 1933 discloses a method wherein filled rigid containers, and separate caps, are passed F. a steam zone at 212.degree. F for the purpose of replacing the air in the headspace of the containers and around the caps with steam. While each cap is being sealed on a container, the container is said to be moved to a cooler zone so that the steam in the headspace condenses thereby reducing the internal pressure below atmospheric pressure.
U.S. Pat. No. 3,871,157 which issued to Domke et al. on Mar. 18, 1975, discloses a bag packaging apparatus wherein bags are severed from a film strip and are thereafter opened, filled and closed while moving through a hood that is divided into compartments. Each compartment is provided with means for independently adjusting the supply of protective gas directed into each compartment. After the bags have been closed they are moved out of the hood and are sealed while in an environment of air.
Johnson et al. U.S. Pat. No. 3,619,975 issued in the United States on Nov. 16, 1971, and discloses a pouch packaging machine which severs pouches from a strip of film at a point outside of a hood. The pouches are first opened while outside the hood with the aid of a splitting bar and a jet of gas such as nitrogen, and are thereafter advanced under a shallow hood having a non-oxidizing gas flowing therein. The pouch is thereafter again widely opened at the filling station by suction cups, is filled with an air-free product and is then advanced to a purging station. While at the purging station a tube is lowered through the product in the filled pouch and directs a non-oxidizing gas into the filled pouch to purge air therefrom. The pouch is subsequently sealed while its upper end is disposed under and aligned with a slot in the floor of the hood.
The present invention provides an improved method of packaging a product in a substantially air-free pouch while moving the pouch through a plurality of processing stations in a tunnel. The method comprises the steps of receiving an empty pouch and maintaining the empty pouch in a closed condition; moving the closed pouch to a tunnel; maintaining an atmosphere of substantially air-free gas in the tunnel by inducing air-free gas to flow through the tunnel; opening the pouch when it is in the air-free gas atmosphere; closing the pouch after it has been opened in the air-free gas atmosphere by squeezing the side walls of the pouch together to thereby purge a mixture of air and the air-free gas from the pouch; thereafter again opening the pouch in said atmosphere; filling the pouch while in said atmosphere; sealing the pouch when in said atmosphere; and discharging the sealed pouch from said tunnel. Preferably, the walls of the pouch are squeezed together after opening the same in the air-free gas atmosphere by dunking the pouch in water. To remove even more headspace air from the pouch, a jet of air-free gas at superatmospheric pressure may be directed into the pouch during the filling of the pouch.
The pouch packaging method of the present invention may comprise the initial steps of receiving an empty pouch and maintaining the empty pouch in a closed condition; applying pressure to the pouch prior to moving the pouch into the air-free gas atmosphere for the purpose of flattening the pouch and squeezing any headspace air out of the pouch; applying a vacuum about the pouch while the pressure is being applied to the pouch to flatten the pouch; and then moving the closed, flattened pouch into the tunnel.